Line Strengths of theP6Multiplets ofGd3+in CaF2at Cubic Sites

The line strengths of the purely magnetic dipole transitions from the nominally ${}_{}{}^8{}_{}{}^{}S_{\frac{7}{2}}^{}{}_{}{}^{}$ ground state of ${\mathrm{Gd}}^{3+}$ to the ${}_{}{}^6{}_{}{}^{}P_{\frac{7}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^6{}_{}{}^{}P_{\frac{5}{2}}^{}{}_{}{}^{}$ multiplets are calculated to be in the ratio of 1.77:1, in agreement with data on the cubic-site spectra of Ca${\mathrm{F}}_2$: ${\mathrm{Gd}}^{3+}$. The intermediate coupling calculation gives a ${}_{}{}^6{}_{}{}^{}P_{\frac{7}{2}}^{}{}_{}{}^{}$ oscillator strength of 6.35×${10}^{-8\mathrm{}}$. Longitudinal and transverse Zeeman measurements confirm the magnetic dipole transition character.